Low power semi-reflective display

ABSTRACT

A semi-reflective display and a method for fabricating and assembling a semi-reflective display are presented, where the display may be comprised of visible light rectifying antenna arrays tuned to four different colors, which when forward biased may use electric power to amplify reflected colored light, and when reversed biased may generate electric power by absorbing light. TFT-tunnel diode logic may be used to control each sub-pixel.

FIELD OF THE INVENTION

Various embodiments of the present invention may pertain to the designand/or manufacture of a low-power semi-reflective display comprised ofpixel sized visible light rectifying antenna arrays.

BACKGROUND OF THE INVENTION

Battery life has become a major issue in portable electronic equipment.One of the highest uses of power in such devices may be the displays.Alternative technologies such as e-ink have been developed, but theyhave neither the performance nor color display precision on the currentLCD displays. Most of the power used in LCD displays may occur fromtheir back lights, and yet 97% of the generated light may be absorbed bythe films and filters in the display itself. Only 3% of the lightactually propagates out of the display as the image seen by the viewer.It would be desirable to have a fast switching reflective display. Theinventor, in U.S. patent application Ser. No. 13/454,155 filed Apr. 24,2012, describes a solar array comprised of an array of visible lightantennas coupled to ultra-high-speed rectifying tunnel diodes. Such anarray may be a light absorbing solar array, when biased to generateelectricity, and light amplifying, when biased to use electricity.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Therefore, various embodiments of the invention may relate to themanufacture and design of a low-power semi-reflective display, which maybe comprised of an array of pixels, where each pixel may be furthercomprised of four sub-pixel sized visible light rectifying antennaarrays, each of which may be individually controlled via TFT-tunneldiode logic, comprising at least one latch, to either absorb lightproducing electric power or consuming electric power to amplify one offour different colors of light.

In other embodiments of the present invention, a display may becomprised of an array of sub-pixels, where each sub-pixel may be furthercomprised of at least two layers of arrays of collinear light frequencyantenna, where the light frequency antenna in the first of the at leasttwo layers of sub-pixels may be perpendicular to the light frequencyantenna in the second of the at least two layers of sub-pixels.Furthermore, solder bumps may perform the electric coupling between theat least two sub-pixel layers and the glass substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will now be described in connectionwith the attached drawings, in which:

FIG. 1 is a cross section of the reflective display according to anembodiment of the invention;

FIG. 2 is a diagram of one pixel area of the first rectifying antennaarray layer, composed of four color sub-pixels, according to anembodiment of the invention;

FIG. 3 is a diagram of one pixel area of the second rectifying antennaarray layer, flipped and rotated to connect with the first layer,according to an embodiment of the invention;

FIG. 4 is a diagram of a single layer of a single color sub-pixel,according to an embodiment of the invention;

FIG. 5 is a diagram of two layers of a single color sub-pixel, accordingto another embodiment of the invention;

FIG. 6 is a diagram of the logical connections of the thin filmtransistor (TFT) to the four pads of each layer of a single colorsub-pixel;

FIG. 7 is a diagram of the wiring of the four sub-pixels of a pixelarea, according to an embodiment of the invention;

FIGS. 8A through 8D depict a process of creating solder bumps for eachrectifying antenna array layer, according to an embodiment of theinvention;

FIG. 9 is a diagram of the cross section of aligning two layers ofrectifying antenna array to the TFT glass layer, according to anembodiment of the invention;

FIGS. 10A and 10B are cross sections of an example of a stencil for thesolder bump pads;

FIG. 11 is a logical diagram of an example of an antenna array,according to an embodiment of the invention;

FIGS. 12A, 12B, and 12C are cross-sections of an example of a stencil inthe Y-direction during its fabrication;

FIGS. 13A, 13B, 13C and 13D are cross-sections of an example of astencil in the X-direction during its fabrication;

FIG. 14 is top cut away view of a section of an example of a stencil;

FIGS. 15A through 15F are cross-sections of an example of an antennaarray during fabrication on a stencil;

FIGS. 16A, 16B and 16C are cross-sections of an example of an antennaarray during its fabrication after removal from a stencil;

FIG. 17 is another diagram of one pixel area of the first rectifyingantenna array layer, composed of four color sub-pixels, according to anembodiment of the invention;

FIG. 18 is another diagram of one pixel area of the second rectifyingantenna array layer, flipped and rotated to connect with the firstlayer, according to an embodiment of the invention;

FIG. 19 is another diagram of the wiring of the four color sub-pixels ofa pixel area, according to an embodiment of the invention;

FIG. 20A is a front view of an example of a portable device containing adisplay; and.

FIGS. 20B and 20C are back views of examples of portable devices.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Examples of embodiments of the present invention will now be describedwith reference to FIGS. 1-20, it being appreciated that the figures mayillustrate the subject matter of various embodiments and may not be toscale or to measure.

In one embodiment of the present invention, two polarizing reflectivelayers may be sandwiched together with a thin film transistor (TFT)glass substrate. Reference is now made to FIG. 1, a cross section of anexample of a display 10 that may have a cover glass layer 14, a firstlayer comprised of sub-pixel sized rectifying antenna arrays 11, asecond layer also comprised of sub-pixel rectifying antenna arrays 12that may be perpendicular to the first layer, a TFT and wiring layer ona clear visible light transmitting glass substrate 13, a light absorbingback cover 15, and other electronics 16, which may include a battery,power supply, and/or pixel clock-driver electronics.

A logical diagram of an example embodiment of a rectifying antenna arrayis shown in FIG. 11. The core of an antenna array may have rows ofantennas 110, separated by power lines 113 and ground lines 114. Thepower and ground lines may be respectively coupled to the antennas byrectifying metal-oxide-metal tunnel diodes 111 and 112. If the antennasare excited by visible light, current may flow from the ground line tothe power line, which may thus produce rectified electrical energy. Forantennas to efficiently receive visible light, it may be advantageousfor them to be either ¼ or ½ of the wavelength of the light beingcaptured, which may depend on whether or not the antenna is coupled toan existing ground plane. In order to produce such small structures,without expensive masking operations, one may create a stencil withwhich to manufacture the antennas.

Most of the antenna array may be constructed on the stencil, such thatpolishing, applying a protective layer, and applying solder bumps to thesub-pixel antenna array pads may then be performed after removing itfrom the stencil.

Reference is now made to FIGS. 12A, B and C, Y-direction cross-sectionsof an example of a stencil during its fabrication, according to anembodiment of the invention. In this case, as shown in FIG. 12B,vertical-sided V-grooves 123 may be etched by resist 120 masking, firsta vertical etch for the power 122 and ground 121 lines, as shown in FIG.12A, and then a V-groove etch 123, as shown in FIG. 12B. The resist maythen be refilled into the V-groove trenches 125 and polished off toexpose the silicon 124, as shown in FIG. 12C. The resist may serve as anetch stop for subsequent X-direction etches.

Reference is now made to FIGS. 10A and 10B, which show examples ofdiagrams of the stencil for the pads. In FIG. 10A, exposing the resist105 may reveal the unmasked silicon 104 to form the pad. Then, in FIG.10B, etching may be performed to form a stencil for a pad. While theremay be no natural etch stop to form the pad stencil, the depth of etch106 may not be critical, but the pad etching may still need to beperformed in two steps, one for all the V-groove pads or just theshallower V-groove pads, and a separate mask for the deeper V-groovepads, for additional (in the case where the first etching is for allpads) or full pad etching (in the case where the first etching is onlyfor the shallower V-groove pads).

Reference is now made to FIGS. 13A, B, C and D, cross-sections of anexample of a stencil in the X-direction during its fabrication. A maskedresist pattern 130 may be formed, which may be followed by a V-grooveetch, as shown in FIG. 13A. Resist may then be reapplied and polishedoff, leaving resist in the existing V-grooves 132, and another V-grooveetch may be performed, creating another set of V-grooves 133, as shownin FIG. 13B. The resist may then be removed, as shown in FIG. 13C, and athin layer of non-adhesion material 134 may be applied to the stencil,as shown in FIG. 13D.

Reference is now made to FIG. 14, a top cutaway view of an example of asection of a stencil, according to an embodiment of the invention. Inthis case, the antenna X-direction V-grooves 140 may be substantiallythe same as those shown in FIG. 13D, and the V-groove trenches 141 and142 may be substantially the same as those 125 shown in FIG. 12C. Thismay serve to facilitate the deposition of the power and ground lines onthe stencil, prior to removing the finished antenna array from thestencil.

Reference is now made to FIGS. 15A through F, cross-sections of anexample of a portion of an antenna array during fabrication on thestencil, according to an embodiment of the invention. Initially, asshown in FIG. 15A, a suitable conductive material, such as nickel, maybe deposited onto the stencil to form the antenna 151, including thebottom of the trenches 152, which may be followed by a thin oxide layer.Next, as shown in FIG. 15B, cover glass may be deposited 153, which maybe at least to the top of the X-direction V-grooves. In one embodiment,a short etch may be added to ensure that the oxide on the ends of theantennas 151 may be exposed. Ideally, the glass and conductive layerbelow it may be chosen to not adhere to the non-adhesion layer 134, asshown in FIG. 13D, on the stencil. Optionally, if the conductivematerials for the power and ground lines may not be easily removed fromthe existing non-adhesion layer, in the next step, a thin layer ofanother non-adhesion material 154 may be deposited, as shown in FIG.15C. Then, the conductive material for the power lines 155 shown in FIG.15D and the ground lines 156 shown in FIG. 15E may be respectivelydeposited and polished off (as needed). Then, a flexible polymer 157,shown in FIG. 15F, may be deposited to form a backing for peeling theantenna array off of the stencil.

Reference is now made to FIG. 16A, a cross-section of an example of anantenna array, peeled from the stencil and flipped over, with an addedcover glass layer, according to an embodiment of the invention.Optionally, this thick cover glass may be polished to remove theunnecessary layers down to the power 162 and ground 161 conductivematerials, as shown in FIG. 16B, and an additional passivation material163 may be added to cover the exposed conductive materials, as shown inFIG. 16C. It should be noted that other fabrication steps may be added,or the steps described herein may be modified as necessary to improvethe yield of the antenna arrays, or for preservation of the stencils.

Reference is now made to FIGS. 8A through 8D, which show an examplefabrication process of aligning two layers of rectifying antenna arrays.In FIG. 8A, both pads for power 82 and ground 83 are shown as widerversions of the same large V-groove metal layers fabricated for therectifying antenna in a sub-pixel. The layers may be peeled off thestencil in the same manner as the solar array technology of U.S. patentapplication Ser. No. 13/454,155, noted above. Electrical separationbetween sub-pixels may occur by not etching the stencil betweensub-pixels such that all the deposited metal may be removed, leavingjust the polymer backing 81 after post-peel polishing. In FIG. 8B, thesame polish and cover polymer 84 may be applied to create the region 88between sub-pixels, but in addition, the pads may be masked to eliminatethe polymer 85 on them. Solder bumps 86 may then be applied, as shown inFIG. 8C. The bottom layer may be flipped over, patterned with anadditional mask and etched to the metal 87 through the original polymerbacking 81, as shown in FIG. 8D.

Reference is now made to FIG. 9, a diagram of an example of across-section of two layers of rectifying antenna array verticallyconnected to a glass substrate containing an array of thin filmtransistors and metal interconnect, according to an embodiment of theinvention. The two layers 90 may be sandwiched together with the glasssubstrate 91 and flipped over such that the upper polymer backing 92 maybe above the glass substrate 91. The sub-pixel pad sizes and spacing maybe consistent with current LCD-TFT technology, making it practical toalign and connect the solder bumps between two layers rectifying antennasub-pixels, thereafter aligning and connecting the two layers of solderbumps to pads on the glass substrate.

Reference is now made to FIG. 2, a diagram of an example of one pixelarea of a first rectifying antenna array layer, composed of four colorsub-pixels, where the colors, red 20, green 21, blue 22 and yellow 23,may be determined by the length of the nickel antenna lines. Referenceis now made to FIG. 3, a diagram of an example of one pixel area of asecond rectifying antenna array layer, flipped and rotated with respectto the organization of the first layer, to vertically connect with thefirst layer. Note that the sub-pixels 30, 31, 32 and 33 may be orientedsuch that their colors vertically align with the sub-pixels 20, 21, 22,and 23 on the first layer.

Reference is now made to FIG. 4, a diagram of an example of a singlelayer of a single color sub-pixel 40 composed of an array of antennas43, which may be, for example, composed of nickel, but which are notthus limited (while “nickel” is discussed below, it should be understoodthat the material is not limited to nickel), between the V-groovegenerated power 41 and ground grids 42, and four pads 44 and 45. Notethat three pads 44 of the four pads may be identically connected to thepower side of the antenna diode array via back-to-back tunnel diodes 46,while the last pad 45 may be connected to the ground grid 42 of therectifying antenna array 40.

Reference is now made to FIG. 5, a diagram of an example of tworectifying antenna array layers 51, 52 aligned vertically with respectto each other to form a single sub-pixel. Light oriented perpendicularto the nickel lines may be transmitted through a single layer of therectifying antenna array. The antenna arrays of the two layers 51, 52may be oriented perpendicular to each other, such that they transmit orabsorb all orientations of light around twice the wavelength of thenickel lines. Note that the identical pads 54 of each layer and theidentical pads 55 of each layer may be vertically aligned.

Reference is now made to FIG. 6, which shows an example of the logicalconnections of the four pads to a sub-pixel rectifying antenna array 60.Each of the three pads 61, 62, and 63 may be connected to back-to-backpairs of tunnel diodes 64, all of which may be connected to an internalnode 65 of the power grid 66 of the rectifying antenna array 60. Theground grid 67 of the rectifying antenna array 60 may be connected to areference voltage pad 68. Together, the three back-to-back tunnel diodepairs 64 may form a tunnel diode latch circuit, which, when a clocksignal on pad 61 transitions from ground to Vcc, may either latch withhigh voltage, near Vcc, or low voltage, near ground, on the intermediatenode 65, which may depend on whether an external TFT 69 may be set tofloat or to ground the pad 62. Note that, using a different logicalarrangement, as would be apparent to one of ordinary skill in the art,such operations may occur on the opposite clock transitions. By settingthe reference voltage pad 68 of the rectifying antenna array 60 to avoltage midway between the high and low latched voltages, the rectifyingantenna array may be either reverse or forward biased. A sub-pixel'santenna array may be reverse biased, which may cause it to act like asolar cell, absorbing light and causing the sub-pixel to look black, ora pixel's antenna array may be forward biased, causing the sub-pixel toglow with its specific color, when stimulated with a correspondingfrequency of light which may be subsequently amplified.

Reference is again made to FIG. 4. The numbers and sizes of theback-to-back tunnel diodes 46 may be adjusted to enhance the oscillationof the associated rectifying antenna array 40, given an appropriatepositive transition of the clock signal on pad 61 when putting thesub-pixel into a forward biased state (as noted above, it isstraightforward to modify the circuitry to use a negative transition,instead of a positive transition).

Reference is now made to FIG. 7, which shows an example of the wiring offour sub-pixels 70, 71, 72, and 73 of a pixel. On a row-by-row basis,for each row of sub-pixels, one clock at a time, the RB 74 and GY 75controls may be set for all columns, and a negative clock pulse may beissued to the RG 76 or BY 77 clock. Once the clock returns high, thestates of all sub-pixels in the corresponding row may be latched untilthe next negative clock pulse resets them (again, while the discussionfocuses on logic using the negative and positive clock pulses in thismanner, by making known modifications to the circuitry, negative andpositive pulses may be reversed). In this manner, the entire panel maybe switched by successively setting all the control lines and issuing anegative clock pulse on each row's clock. For each row, the Red 70 andGreen 71 sub-pixels may be switched together, with a Red-Green clockpulse on the RG 76 clock line, distinctly separately from the Blue 72and Yellow 73 sub-pixels, which may be switched together, using aBlue-Yellow clock pulse on the BY 77 clock line. One pad 68 of eachsub-pixel may be connected to a common set of voltage reference lines79, and the last pad 63 of each sub-pixel may be connected to a commonset of ground lines 80 (note that pads 63 and 68 are shown in FIG. 6).

It is further contemplated that additional circuitry may be coupled tothe reference voltage lines to both allow the reverse biased sub-pixelsto power the forward biased sub-pixels and to extract the residual powerfrom the display when the number of reverse biased sub-pixelssufficiently exceeds the number of forward biased sub-pixels to generatepower.

It is also contemplated that the reference voltage and/or clock voltagesmay be varied to increase the amount of light amplification of theforward biased sub-pixels. Furthermore, these voltages may bedynamically adjusted in a manner that may be related to the measuredamount of power detected from the display, thereby dynamically adjustingthe brightness of the display in relation to the amount of ambientlight.

It is also contemplated that the reference voltage lines may be combinedto form an array of separate grids, where each grid may comprise anM-by-M array of pixels, such that measurement of the power generated byeach grid may be used to detect the presence of finger shadows for usein interactive display operation. Power from reverse biased pixels maydrop off when a finger blocks the ambient light to the array of pixelswithin the measured grids. As such, the grids may be comprised ofsufficient pixels to determine the center of the finger shadow.

Alternatively, in yet another embodiment of the invention, the first andsecond antenna layers may be connected to separate reference voltagelines or grids, which may thereby allow the presence of fingers to besensed by differential current on the separate reference voltages linesdue to capacitive changes in the pair of antenna layers.

Reference is now made to FIG. 17, another example diagram of one pixelarea of a first rectifying antenna array layer, composed of fourdifferent color sub-pixels, according to an embodiment of the invention.In this case, the adjacent sub-pixels 170 and 174 may be rotated andflipped such that the ground grids 42, as seen in FIG. 4, are adjacentto each other. By connecting 172 the adjacent ground grids together, onepad 173 may be externally connected to a reference voltage line or gridfor each pair of horizontally adjacent sub-pixels. The other pad 171 maybe disconnected, which may allow for vertical connections to a glasssubstrate via solder bumps 93, e.g., as seen in FIG. 9.

Reference is now made to FIG. 18, another example diagram of one pixelarea of a second rectifying antenna array layer, flipped and rotated toconnect with the first layer, according to an embodiment of theinvention. In this case, the adjacent sub-pixels 180 and 184 may berotated and flipped such their ground grids are also adjacent andconnected 182 to each other, and as with FIG. 3, their antennas may beperpendicular to the sub-pixels in FIG. 17. Similar to FIG. 17, one pad183 may be externally connected to a reference voltage line or grid foreach pair of horizontally adjacent sub-pixels 180 and 184. The other pad181 may be disconnected, which may allow for vertical connections to aglass substrate, e.g., via solder bumps 93, as seen in FIG. 9. Note thatthe disconnected pads 181 and 171 of a given layer, may vertically alignwith the other layer's connected pads 173 and 183.

Reference is now made to FIG. 19, another diagram showing an example ofthe wiring of the four color sub-pixels of a pixel area, according to anembodiment of the invention. In this case, the clock 193 and ground 190lines may be organized to allow the voltage reference for the firstlayer 191 to be perpendicular to the voltage reference for the secondlayer 192. In this manner, separate reference voltage grids may becreated to measure the capacitance between the two layers, which may bedone on an M-by-M pixel basis.

In addition, when a portable device containing such a low-powersemi-reflective display turns off its display to conserve power, thedisplay may be put into a configuration such that all sub-pixels maygenerate power to recharge the batteries of the portable device.

It is also contemplated that when the electronics in a portable deviceare powered off or in a sleep mode, the display may also remain in aconfiguration to measure the capacitance on each M-by-M pixel grid,which may be used to enable sensing when a user touches the screen, tothereafter permit the device to turn on the electronics and the displayfor viewing. Furthermore, when turning on the electronics from a poweredoff state, a start up procedure may be initiated, which may include anunlocking method comprising the detection of a dynamic sequence offinger movement around the screen, matching such a sequence of movementsto a predetermined sequence, and if successful, finishing the start upprocess, or if not successful, terminating the process and powering thedevice back off. Such a predetermined sequence may be a standard factoryprogrammed sequence, a unique factory programmed sequence, documented tothe purchaser, a stored user generated sequence, or a temporary usergenerated sequence. In this manner, the portable device may not requirebuttons or switches to power on or off the device; rather it may besufficient to have a locked back battery compartment and an automaticpower on sequence when reconnecting the disconnected batteries. Such apower cycling may erase any temporary user generated sequence, requiringan earlier stored sequence to be used to start up the device. Any or allof these predetermined sequences may be used to unlock the device. Also,when powering on a portable device in low ambient light, detected by asufficiently low level of power generated by the display, the device mayautomatically turn on auxiliary light(s) to aid in seeing the portabledevice and its display.

It is further contemplated that when the portable device powers off thedisplay, if the level of power generated by the display falls below somethreshold, the display may be electrically disconnected to minimize theconsumed standby power, leaving a single M-by-M voltage grid in powergeneration mode to detect either an increase in the ambient light thatis sufficient to turn the screen back on, or to detect a change in thegrid's capacitance indicating a touch, which may thereby cause thescreen to power back on and begin a start-up process.

Finally, such techniques when combined may allow suitably storedportable devices to seldom, if ever, need external recharging. As such,with adequately robust batteries and artificially lit or transparentstorage containers, such portable devices may be completely sealed,relying solely on wireless communications and the touch sensitivedisplay for external communication.

Reference is now made to FIGS. 20A and 20B, examples of front and backviews of a portable device. Note that the display 201 may be embedded inthe front half of a plastic case 202, which may be glued to the backhalf of the plastic case 203, such that no external components, buttons,connectors, compartments or antennas may protrude through the enclosure.The display may be a low power semi-reflective display as describedabove. Optionally, other devices, such as a camera or light sensor 204,may be embedded behind other smaller openings, e.g., in the back of theplastic case 203. Moving parts, such as rotating storage, microphones,speakers and/or other mechanical devices may be connected via Bluetooth®or other suitable wireless communication techniques. Power may beobtained from the low power semi-reflective display embedded in thefront of the plastic case, and may be stored in a rechargeable batteryinternal to the device.

Reference is now made to FIG. 20C, the back view of another example of aportable device. Alternatively, the front half of the case may have atraditional touch activated reflective display, and the back half of thecase 205 may have an embedded solar cell 206 from which power may beobtained to be stored in a rechargeable battery internal to the device.

Such portable devices may become increasingly attractive due to fallingcosts of and improvements in batteries, electronics, displays and/orsolar cells, along with the additional cost reduction and increasedreliability of the system by eliminating mechanical connections,simplifying the enclosure, removing movable parts, and integrating arecharging battery. By being completely sealed, such devices may bedesigned to be rugged, waterproof, and/or disposable.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and sub-combinations of various featuresdescribed hereinabove as well as modifications and variations whichwould occur to persons skilled in the art upon reading the foregoingdescription and which may be not in the prior art.

I claim:
 1. A display comprising: a glass substrate containinginterconnect and thin film transistors; an array of sub-pixels; at leasttwo layers of light frequency antennas, wherein the light frequencyantennas in a first layer of the at least two layers of light frequencyantennas are perpendicular to the light frequency antennas in a secondlayer of the at least two layers of light frequency antennas; and for arespective sub-pixel, one or more solder bumps configured toelectrically couple the at least two layers of light frequency antennasto the glass substrate.
 2. The display as in claim 1, further comprisingcircuitry configured to individually control a respective sub-pixel tobe in one of two modes.
 3. The display as in claim 2, wherein thecircuitry comprises at least one latch.
 4. The display as in claim 3,wherein the latch is a tunnel diode latch.
 5. The display as in claim 2,wherein, in a first mode a respective sub-pixel absorbs light, and in asecond mode, a respective sub-pixel amplifies ambient light.
 6. Thedisplay as in claim 5, wherein the respective sub-pixel in the firstmode converts light into electric power and in the second mode convertselectric power into light.
 7. The display as in claim 1, wherein theantennas for a respective sub-pixel are all tuned to a particular lightfrequency of a set containing plural light frequencies.
 8. The displayas in claim 7, wherein the set containing plural light frequenciescomprises light frequencies corresponding to: red, green, blue andyellow.